Avian Influenza A(H5N1) Virus in Egypt

Abstract

In Egypt, avian influenza A subtype H5N1 and H9N2 viruses are enzootic in poultry. The control plan devised by veterinary authorities in Egypt to prevent infections in poultry focused mainly on vaccination and ultimately failed. Recently, widespread H5N1 infections in poultry and a substantial increase in the number of human cases of H5N1 infection were observed. We summarize surveillance data from 2009 through 2014 and show that avian influenza viruses are established in poultry in Egypt and are continuously evolving genetically and antigenically. We also discuss the epidemiology of human infection with avian influenza in Egypt and describe how the true burden of disease is underestimated. We discuss the failures of relying on vaccinating poultry as the sole intervention tool. We conclude by highlighting the key components that need to be included in a new strategy to control avian influenza infections in poultry and humans in Egypt.

Keywords: Egypt; avian influenza; influenza; respiratory infections; subtype H5N1; surveillance; vaccination; vector-borne infections; viruses.

Figure 1

Monthly positivity rate of poultry infection with avian influenza viruses (all types), Egypt, August 2010–December 2014. A seasonal pattern is shown by sharp increases in rates during colder months (November–March). Emergence of H9N2 virus in poultry and an increase in human H5N1 cases are indicated.

Figure 2

Monthly positivity rate of infection with avian influenza viruses (all types), Egypt, February 2013–December 2014. As in Figure 1, a seasonal pattern is shown by sharp increases in rates during colder months (November–March).

Figure 3

Subtypes of influenza A viruses detected in poultry by using reverse transcription PCR, by month, Egypt, February 2013–December 2014.

Figure 4

Phylogenetic tree of the hemagglutinin genes of avian influenza subtype H5N1 viruses isolated in Egypt during 2006–2014 and reference isolates from GenBank. Phylogenetic analysis was conducted by using the neighbor-joining algorithm with the Kimura 2-parameter model. Strain A/bar-headed goose/Qinghai/3/2005 was used as the root for the tree, and the reliability of phylogenetic inference at each branch node was estimated by the bootstrap method with 1,000 replications. Evolutionary analysis was conducted by using MEGA6 (http://www.megasoftware.net). A) Clade 2.2 viruses from 2006–2008 are shown in blue, subclade 2.2.1.1 viruses are shown in green, and clade 2.2.1 viruses are shown in red. B) Human viruses sequenced for this study are shown in blue. Boldface red font indicates avian viruses isolated in 2014 and sequenced for this study; lightface red font indicates other viruses from GenBank. *Indicates that 2014 viruses were grouped in 1 lineage. Scale bars indicate nucleotide substitutions per site.

Figure 5

Antigenic cartography of reactivity of highly pathogenic avian influenza A(H5N1) virus isolates from Egypt, 2006–2014. The map was produced by using hemagglutination inhibition assay data generated with a panel of monoclonal antibodies and by using AntigenMap (http://sysbio.cvm.msstate.edu/AntigenMap). One unit (grid) represents a 2-fold change in the assay results. Each mark on the map represents results for 1 isolate.

Figure 6

Human cases of avian influenza A(H5N1) virus infection and associated deaths, Egypt, 2006–2015. Data for 2015 include cases confirmed in January and February only. For reference, the emergence of H9N2 virus in poultry is shown (arrow).

Figure 7

Cross-reactivity of antisera raised against commercial and experimental inactivated H5 vaccines against avian influenza A(H5N1) virus isolates from Egypt, 2006–2014. Antisera from chickens immunized with the H5 vaccines were tested by using a hemagglutination inhibition (HI) assay against virus isolates from Egypt during 2006–2014 (x-axis). Egy, Egypt; Guang, Guangdong; rg, reverse genetics–engineered reassortant.